Along with the emergence of smart devices and network applications, a user may access various network applications through application clients installed in a terminal device. To conduct an online transaction using a network application, the user is often required to perform identity authentication, member registration, or the like. For example, an application server may send verification information to the terminal device possessed by the user in a text message or an email. The user may then input a verification code carried in the verification information to pass security verification of the application server and obtain access to the network application.
The verification code carried in the verification information generally includes simple numerals. For example, during an online banking transaction, a server of the banking system may send a verification text message formed by 6 digits of numerals to the application client, and after the user inputs the 6 digits of numerals correctly, the user can complete the online banking transaction. However, since simple plaintext numeral information is included in the verification information, a malicious third party can easily steal the verification information through a Trojan. The conventional security verification is often found to be unreliable and produces a low level of security for accessing the network applications.